The present invention relates to tire pressure maintenance systems and, in particular, it concerns five subsystems whose synergy results in a comprehensive tire pressure maintenance system.
Tire Pressure Monitoring Systems (TPMS) are now a required safety feature on all new cars sold in the US. Virtually all TPMS designs in the marketplace involve a sensor that is installed within the interior of the rim and attached to the base of the valve stem. The only way to access the sensor is to remove the tire from the wheel. Removing the tire from the wheel is too difficult a task for the general public. Even the Do-It-Yourself enthusiast would require a highly specialized, expensive tire removal tool to access the sensor.
The ability to access the sensor is important due to an inherent problem in the TPMS designs in the marketplace. Currently, most sensors have internal batteries that are housed and sealed within the sensor unit. These batteries have a limited life, which limits the life of the sensor. When the battery dies, the car owner may be forced, depending on local safety standards, to replace the sensor and have it reinstalled. In lieu of such legislation, the owner may still decide to replace the TPMS unit for reasons of personal safety. This is a significant expense to the car owner, which is triggered by the recurring need to replace a relatively inexpensive battery. The need of the designs currently in use to regularly replace an inexpensive part has converted the otherwise durable monitor sensor to a disposable high-cost item.
Additionally, some commercial and military vehicles have on-board air compressors that re-inflate under-pressured tires. There are also, for consumer applications, self-inflating tires that are specially designed to maintain a constant target tire pressure. As well, the design and introduction of run-flat tires allow a driver to continue driving for a limited distance at a limited speed with a compromised or flat tire that can no longer maintain adequate air pressure.
Self inflating tires (SIT) typically utilize an external delivery system to re-inflate tires. Commercial vehicle and military applications use on-board air compressors that feed air through a hose that delivers air to the tire. Such a configuration is not practical for automobile and light vehicle applications.
A recent innovation in self-inflating tires for automobiles involves the use of a peristaltic pump that is placed between the lip of the tire and the wheel rim. As the wheel rotates it forces air into the tire and is regulated by a pressure sensitive valve. While an elegant solution for automobile and light vehicle applications, this design requires either customized rims or tires that can accommodate or integrate the peristaltic pump.
Run-flat tires are designed to allow a driver to continue driving after a tire has been compromised. Three basic designs are: self-sealing, self-supporting and auxiliary-supported.
A self-sealing tire uses either a special internal liner or a sealant to repair a minor puncture. The effectiveness of this design is limited to preventing or slowing air escaping after incurring a small tire puncture or hole. As well, self-sealing tires often use sealants that can damage tire pressure monitoring sensors, which are now a required feature on all new vehicles.
A self-support tire utilizes a thicker side wall that is designed to support the weight of a car when the tire is deflated. The modified design negatively affects the handling characteristics of the tire. After sustaining a flat, these tires can only be driven for a limited distance at a limited speed. As well, these tires typically have a 20% to 40% weight penalty. Furthermore, driving in a deflated state compromises the tires integrity and they cannot be repaired or reused.
An auxiliary-supported tire has a ring of weight-bearing material that attaches to the interior of the rim and supports the weight of the car when the tire is deflated. This material is taller than the side walls of the rim but not tall enough to touch the inner circumference of a properly inflated tire. This design requires both special tires and often special rims to accommodate the auxiliary support. This design also attracts a significant weight penalty and can only be driven for a limited distance at a limited speed.
As mentioned above, Tire Pressure Monitoring Systems (TPMS) are now a required safety feature on all new cars sold in the US. Virtually all TPMS designs in the marketplace involve a sensor that is installed within the interior of the rim which broadcasts real-time tire pressure data to the car's electronic information network. In some higher end vehicles the tire pressure data is presented graphically via an on-board screen that displays a visual image of each wheel's position and tire pressure. However, in many cars the data displayed is reduced to a single indicator light that signals when one or more of the tires are under-inflated by 25% or more. Although this design satisfies the safety regulations mandated under the TREAD Act, a simple warning light does not convey the actual tire pressure, the number of wheels affected or the wheel position of the under-inflated tire(s). It also fails to signal over-inflation or any under-inflation below the 25% threshold. Consequently, a warning light does not enable the driver to monitor and manage optimal tire pressure, which impacts both safety and fuel efficiency.
Once the warning light goes on, the driver must still use a tire pressure gauge to determine which tires need re-inflating. Even the higher cost systems that display tire pressure and positional information must still rely on a pressure gauge when inflating the tires. Since the displays are built into the car's dashboard they are out of view when the tires are being inflated and so an air pressure gauge must be used to monitor the tire pressure. Typically, portable mechanical gauges and service station air hoses can be 10% to 15% inaccurate.
To address these problems the proposed solution is i) an affordable alternative to identify each tire's pressure and ii) to accurately inflate each tire to optimal inflation by automatically setting the target tire pressure to its recommended inflation level and either iii) a) signaling once the target air pressure is achieved or iii) b) delimiting the air pressure to the recommended target by using an electronically controlled regulator. Furthermore, iv) each wheel's tire pressure can be viewed remotely (outside of the car's cabin) and wirelessly without the need to physically attach anything to the wheel assembly or the need to turn on the car.
There is therefore a need for a TPMS in which the sensor is mounted in the interior region of the tire and the battery is mounted on the exterior of the tire. To augment such a TPMS, there is also a need for a tubular dry cell battery for use with the TPMS of the present invention. There is additionally a need to re-inflate a tire once the air pressure falls outside an ideal target air pressure range. There is further a need to provide a self-inflating run-flat tire. There is also a need for a device for monitoring tire pressure during inflation that utilizes the Tire Pressure Monitoring System (TPMS) associated with the vehicle.
While there is therefore a need for each of the sub-systems as mentioned directly above, the synergy of these systems results in the need for a comprehensive tire pressure maintenance system that incorporates all of the sub-systems of the present invention. It will certainly be appreciated that benefit will be derived from substantially any combination of fewer than all of the sub-systems of the present invention.